Shaft lock for power tool

ABSTRACT

A power tool includes a tool shaft and a mechanism for restricting movement of the tool shaft. The mechanism includes a pin configured to engage the tool shaft to restrict movement of the tool shaft and a member provided adjacent the tool shaft and fastened to a housing of the power tool The member includes an aperture through which the pin extends when the pin engages the tool shaft.

BACKGROUND

The present invention relates generally to the field of power tools. More specifically, the present invention relates to hand-held power tools that include a mechanism for locking a shaft of the power tool to allow attachment of accessories to the shaft.

Hand-held power tools generally include a housing and a motor contained within the housing. The motor is configured to move a tool bit or other cutting accessory at high speeds to form cuts in a workpiece (e.g., a piece of wood, drywall, tile, etc.). For example, a hand-held rotary cutting tool such as that disclosed in U.S. Pat. Nos. 5,813,805 and 6,443,675 to Kopras et al. (the disclosures of which are incorporated by reference herein in their entirety) is configured to rotate a helical or spiral cutting tool bit that includes a sharp cutting edge wrapped in a helix around the longitudinal axis of the bit. According to this example, the tool is configured to allow the formation of cuts in a workpiece by moving the tool in a direction perpendicular to the axis of rotation of the bit (i.e., the tool is arranged normal to the workpiece surface and moved parallel to the surface of the workpiece to allow the edges of the bit to remove material from the workpiece).

To secure an accessory such as a tool bit or other cutting tool accessory to a shaft of the power tool, it is advantageous to provide a mechanism which restrains or prevents rotation of a tool shaft. Such a mechanism should be relatively simple and efficient to operate, and should continue to be useful throughout the life of the tool. For example, it may be desirable to provide a mechanism that allows a user of the power tool with one hand to stop rotation of the tool shaft while inserting a cutting accessory or the like with another hand. Known mechanisms for restricting or stopping the rotation of a power tool shaft do not realize certain advantageous features as will be described below with respect to the present invention.

It would be advantageous to provide an improved system for attaching tool bits and other accessories to a power tool. It would also be advantageous to provide a power tool having a shaft lock system that is reliable and resistant to wear with continued usage. It would be desirable to provide a power tool having any one or more of these or other advantageous features as may be apparent to those reviewing this disclosure.

SUMMARY

An exemplary embodiment of the invention relates to a power tool that a tool shaft and a mechanism for restricting movement of the tool shaft. The mechanism includes a pin configured to engage the tool shaft to restrict movement of the tool shaft and a member provided adjacent the tool shaft and fastened to a housing of the power tool. The member includes an aperture through which the pin extends when the pin engages the tool shaft.

Another exemplary embodiment of the invention relates to a power tool that includes a rotatable shaft having an opening provided therein and a device for preventing rotation of the shaft during attachment of an accessory to the shaft. The device includes a rod configured for selective insertion into the opening to prevent rotation of the shaft and a plate having an aperture provided therein through which the pin extends during insertion of the rod into the opening. The plate is fastened to the power tool and is configured to transmit a load from the rod when a user attaches an accessory to the shaft.

Another exemplary embodiment of the invention relates to a power tool having a mechanism for preventing free rotation of a tool shaft during attachment of an accessory to the tool shaft. The power tool includes a tool shaft having an aperture extending at least partially through the tool shaft in a direction transverse to a central longitudinal axis of the tool shaft. The power tool also includes a pin configured for selective movement between a first position in which a portion of the pin is in the aperture and a second position in which the portion of the pin is not in the aperture. The power tool further includes a metal member provided adjacent the tool shaft and having an aperture through which the pin extends in the first position, the metal member secured to the power tool with at least one fastener. The tool shaft is prevented from freely rotating when the pin is in the first position and is not prevented from freely rotating when the pin is in the second position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a hand-held power tool according to an exemplary embodiment.

FIG. 2 is another perspective view of the hand-held power tool shown in FIG. 1.

FIG. 3 is an exploded perspective view of a shaft lock mechanism for a power tool according to an exemplary embodiment.

FIG. 4 is a perspective view of a locking plate included in the shaft lock mechanism according to an exemplary embodiment.

FIG. 5 is a partial cutaway view of a portion of the power tool shown in FIG. 1 according to an exemplary embodiment.

FIG. 6 is a partial cutaway view of a portion of the power tool shown in FIG. 1 having a locking plate such as that shown in FIG. 4 installed according to an exemplary embodiment.

FIG. 7 is a partial cutaway view of a portion of the power tool shown in FIG. 1 having a locking plate such as that shown in FIG. 4 and a tool shaft installed according to an exemplary embodiment.

FIG. 8 is a perspective view of a locking plate for use with a power tool according to another exemplary embodiment.

FIG. 9 is a partial cutaway view of a portion of a power tool similar to that shown in FIG. 1 according to an exemplary embodiment.

FIG. 10 is a partial cutaway view of a portion of the power tool shown in FIG. 9 having a locking plate such as that shown in FIG. 8 installed according to an exemplary embodiment.

FIG. 11 is a partial cutaway view of a portion of the power tool shown in FIG. 9 having a locking plate such as that shown in FIG. 8 and a tool shaft installed according to an exemplary embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A hand-held power tool 100 in the form of a rotary cutting tool is shown generally in FIGS. 1 and 2. It should be understood that although the present invention will be described in detail herein with reference to the exemplary embodiment of a rotary cutting tool 100 shown in FIGS. 1 and 2, the present invention may be applied to, and find utility in, other types of hand-held power tools as well (e.g., drills, saws, routers, etc.) and therefore, the scope of the invention is not limited to application in the rotary cutting tool 100.

The tool 100 includes a housing or casing 110 to which a handle 120 is attached. The housing 110 is made of an electrically insulating material such as hard plastic according to an exemplary embodiment. The housing 110 is generally cylindrical in shape, and may be formed as two or more molded pieces which are joined together to form the housing 110 in a conventional manner, such as using fasteners, an adhesive, welding, or a combination thereof.

A motor (not visible in FIGS. 1 and 2) is enclosed within the housing 110. The motor receives electrical power from a battery pack 130 selectively coupled to the power tool at an end thereof. A member or element 132 is provided to allow the battery pack 130 to be removed when the member 132 is depressed. According to an exemplary embodiment, the battery pack 130 includes one or more rechargeable batteries and has a fully charged voltage of between approximately 12 and 24 volts. According to a particular exemplary embodiment, the battery pack has a fully charged voltage of approximately 18.6 volts. The battery pack 130 may include any suitable type of batteries, such as nickel-metal hydride or lithium-ion batteries.

The motor is turned on and off by a power on/off switch 140. According to an exemplary embodiment, the switch 140 is pulled away from the housing 110 to activate the motor. The motor may be configured to operate at a single speed (e.g., a speed between approximately 15,000 and 30,000 rpm) or a number of speeds (e.g., speeds of 15,000 rpm, 20,000 rpm, and 30,000 rpm). In a case where the motor is capable of operating at multiple speeds, the switch may include multiple positions corresponding to the desired motor speed.

To set the depth of cut to be made by the tool 100, an adjustable depth guide assembly 160 may be provided. The depth guide 160 is attached to the housing 110 adjacent the location where the motor shaft emerges from the housing 110.

As shown in FIG. 1, a depth guide bracket 162 is selectively attachable to the housing 110, and may be attached to the housing 110 in any conventional manner. For example, the depth guide bracket 162 may be formed to have a split collar structure and a cam closing mechanism 164 (e.g., an over-center latch) which is operated to close the collar tight around the end of the tool housing 110, and which may be operated to loosen the collar to remove the bracket 162 from the housing 110.

The depth of cut of the power tool 100 may be set by moving an extending portion 166 of the depth guide 160 in a direction along the longitudinal axis of the tool bit 154. A locking mechanism may then be used to lock the extending portion 166 in a fixed position relative to the bracket 162 to securely fix the depth guide 160 in place. The locking mechanism may be implemented as a cam lever, as a threaded nut or a screw, or as any other suitable type of device or mechanism.

The motor of the tool 100 drives a motor shaft to which a device or mechanism 150 is coupled for securing a cutting accessory (e.g., a helical cutting tool bit or other accessory) to the motor shaft. As shown in FIG. 1, the device 150 includes a collet (not shown) and a collet nut 152 for securing a tool bit 154 to the motor shaft of the tool 100. According to an exemplary embodiment, the tool bit 154 includes a cutting edge wrapped around the axis of the bit in a helix or spiral. This cutting edge is designed such that the tool bit 154, when rotated at high speed, will cut through a workpiece in a direction substantially perpendicular to the axis of the bit.

To secure the tool bit 154 to the motor shaft, a shank of the bit is inserted into a central aperture of the collet, after which the collet nut 152 is tightened. A shaft lock button or cap 156 is provided as part of a shaft lock mechanism (described in greater detail below with reference to FIGS. 3-11) to restrict or prevent rotation of the motor shaft when the collet nut 152 is being loosened and tightened. As the collet nut 152 is tightened down on the threaded end of the shaft, the collet is compressed within the collet nut 152 between a partially closed end of the collet nut 152 and the shaft. The collet is slotted and has tapered ends such that when the collet is compressed between the collet nut 152 and the shaft, the collet is compressed radially, causing the central aperture of the collet to close tightly around the shank of the tool bit. To remove the bit from the motor shaft, the collet nut 152 is loosened until the bit can be removed easily from the central aperture of the collet.

FIGS. 3-7 illustrate features of the a shaft lock mechanism 200 according to an exemplary embodiment. The tool 100 includes a shaft 170 having a rotational (i.e., a central longitudinal) axis. The shaft 170 also includes an aperture 172 provided therein. The aperture 172 has a size and shape configured to receive therein a pin or rod 210 that is coupled or attached to the shaft lock button 156 (the end of the pin may include a taper or chamfer for easier insertion into the aperture 172, as shown in FIG. 3). A user of the tool 100 may depress or push the shaft lock button 156 while slowly rotating the shaft 170 until the pin 210 is received within the aperture 172, at which point rotation of the shaft 170 is restricted or prevented due to the interaction of the pin 210 and the aperture 172. The shaft lock button 156 and pin 210 are biased away from the shaft by a spring 212 which is provided around the pin 210 (i.e., the pin is received within the coil of the spring 212). According to other exemplary embodiments, the spring may be provided such that the pin is not received within its coil (e.g., the spring may be adjacent the pin and spaced away therefrom). According to an exemplary embodiment, the spring 212 keeps the pin 210 from interfering with the rotation of the shaft when the user does not intentionally want to do so (e.g., it keeps the pin disengaged from the shaft).

A member or element 220 in the form of a retaining plate is provided within the housing 110 according to an exemplary embodiment. The member 220 includes a hole or aperture 222 configured for receiving therethrough the pin 210 when the pin 210 is depressed and engages the aperture 172 in the shaft 170. According to an exemplary embodiment, the member 220 may be made or formed of a metal such as steel, zinc, aluminum, or bronze. According to other exemplary embodiments, the member 220 may be made or formed of a polymer, carbon fiber, composite material, or any other suitable material. The member has a thickness of approximately 1.5 millimeters and the aperture 222 has a size and shape complementary to that of the pin 210. According to other exemplary embodiments, the thickness of the member may vary to suit the load it needs to carry or transmit in a particular application.

According to an exemplary embodiment, the member 220 guides the pin 210 to aid in the alignment of the pin 210 with the aperture 172 in the shaft 170. The member 220 acts to transmit the load applied from the pin 210 to relatively strong regions of the housing 110 of the tool 100 when the shaft lock mechanism 200 is used to install or remove an accessory such as a tool bit. By using a metal material (or any other suitable material with similar properties) to form the member 220, the member 220 can better transmit the loads and has a higher yield strength than polymeric or other materials which might otherwise be used. Further, the close proximity of the member 220 to the shaft 170 acts to reduce forces applied to both the member 220 and the pin 210 when the shaft lock mechanism 200 is utilized, thus reducing the occurrence of failures or deformations of components of the tool 100. For example, according to an exemplary embodiment, the distance between the rotational axis of the shaft 170 and the center of the member 220 is approximately 10.5 millimeters (e.g., 10.62 millimeters according to a particular exemplary embodiment).

According to an exemplary embodiment, the housing 110 of the tool 100 is molded or formed in two clam shell halves. As shown in FIG. 3, a first clam shell 112 includes features 114 and 116 for coupling the clam shell 112 to a second clam shell (not shown). The features 114 and 116 are configured for receiving therein a fastener such as a screw or bolt to secure the clam shells together when assembly of the tool is complete. Advantageously, the shaft lock mechanism 200 is retained substantially entirely within one of the clam shell halves (e.g., as shown in FIG. 7, the shaft lock mechanism 200 is retained within the clam shell 112).

According to an exemplary embodiment, the member 220 includes an aperture or hole 224 for fastening or securing the member 220 to the housing 110. As shown in FIG. 5, the clam shell 112 includes a feature 118 configured to receive a fastener such as a screw or bolt for securing the member 220 to the clam shell 112. While FIG. 4 illustrates a member 220 that includes a single aperture 224 for fastening the member 220 to the housing 110 of a tool 100, according to other exemplary embodiments, more than one aperture may be provided for securing the member to a tool housing. For example, according to other exemplary embodiments, two or more apertures may be provided for receiving fasteners which secure the member to a power tool housing. According to another exemplary embodiment, the member 220 may be fastened to the housing 110 without the use of a discrete fastener. For example, the member may be hot staked to the housing (e.g., a pin-like extension integrally formed with the housing may be melted or deformed after it is provided through the aperture 224 to hold the member 220 in place).

In operation, the member 220 is positioned within the clam shell 112 between a number of ribs (shown in FIG. 6 as ribs 113, 115, 117, and 119) which act to prevent or restrain lateral movement of the member 220 within the clam shell 112 and to transmit loads from the member 220 to the housing 110. To secure the member 220 within the housing 110, a fastener is inserted through the aperture 224 provided in the member 220 and into the feature 118 provided in the clam shell 112 to secure the member 220 within the clam shell 112.

An end 226 of the member 220 may be tapered or chamfered to aid in assembly of the shaft lock mechanism 200. The tapered end 226 may be provided below a feature 121 (FIG. 6) provided in the housing 110 which may act to secure the tapered end 226 in place in the tool 100. As shown in FIG. 6, the member 220 is thus restrained at a first end by the feature 121 and at the other opposite end by a fastener inserted through the aperture 224 in the member 220.

As shown in FIG. 6, the member 220 is provided over the shaft lock button 156. According to an exemplary embodiment, the pin 210 does not extend through the aperture 222 in the member 220 unless the button 156 is depressed by a user (e.g., to overcome the spring force provided by the spring 212). According to another exemplary embodiment, a portion of the pin 210 is provided within the aperture 222 prior to depression of the button 156 by a user (e.g., the end of the pin 210 is within the aperture 222 when the button is in the “rest” state such that the wall of the aperture 222 acts as a guide for the pin 210).

As shown in FIG. 7, the shaft 170 is then provided adjacent the member 220, after which the second clam shell half of the housing 110 may be coupled to the clam shell 112 by fasteners inserted into the features 114 and 116. As shown in FIG. 7, the shaft 170 may be restrained or prevented from moving (e.g., prevented from rotating) by depressing the shaft lock button 156 such that the pin 210 extends into the aperture 172 provided in the shaft 170. According to an exemplary embodiment, the aperture 172 extends entirely through the shaft 170. According to other exemplary embodiments, the aperture in the shaft may extend only a portion of the way through the shaft.

While FIGS. 3-7 illustrate the use of a member 220 that has a relatively flat or planar configuration, according to other exemplary embodiments, other configurations may be utilized. For example, as shown in FIGS. 8-11, a member 320 may be provided that includes a flat or planar portion 330 having two members or elements in the form of legs 332, 334 which extend at substantially right angles to the flat or planer portion 330. Members or elements 336 and 338 in the form of feet extend from the members 332 and 334, respectively. According to an exemplary embodiment, the legs 332, 334 are biased outward (e.g., approximately 2 degrees) to provide a better fit in the housing 110 as the tool 100 is assembled.

Apertures or holes 324 and 326 may be provided in the feet 336 and 338 for securing the member 320 within a tool housing. Similar to the member 220, the member 320 includes an aperture or hole 322 through which the pin 210 of the shaft lock mechanism 200 may extend to engage the aperture 172 provided in the shaft 170. An optional aperture or hole 328 may also be provided in the flat or planar portion 330 for receiving therein a feature 329 in the housing 110 (e.g., a boss) to aid in positioning the member 320 within the housing 110.

As shown in FIG. 9, according to an exemplary embodiment, the shaft lock button 156, pin 210, and spring 212 are provided within the clam shell 112. The boss 329 is provided for aiding in the positioning of the member 320 upon insertion of the member 320 in the clam shell 112 and retaining the member 320 during assembly as shown in FIG. 10. Retention of the member 320 in place during assembly is necessary due to the fact that the member 320 is installed over the button 156 and compresses the spring 212. A fastener such as a screw (not shown) may be driven into the boss 329 to secure the member 320 to the housing. According to another exemplary embodiment, the boss may be hot staked or deformed to retain the member 320 during assembly. Ribs 123 and 125 may also be provided to assist in positioning the member 320 and for transmitting loads from the pin 210 to the housing 110 of the tool 100.

The apertures 324 and 326 provided in the feet 336 and 338, respectively, are configured for alignment with the features 114 and 116 provided in the clam shell 112. According to an exemplary embodiment, the apertures 324, 326, and 338 provided in the member 320 have a generally oblong or oval shape to allow flexibility in positioning the member 320 within the housing 110.

As shown in FIG. 11, the shaft 170 is then provided within the housing 110 along with a bearing 174 for aiding in the rotation of the shaft 170. It should be noted that while not illustrated in FIGS. 3-7, a bearing such as the bearing 174 may also be provided in the embodiment shown in FIGS. 3-7.

One advantageous feature of providing a member 320 such as that shown in FIG. 8 is that such a member includes features which add rigidity and allow for the provision of retaining screws in a location other than a plane shared with the flat or planar portion 330 of the member 320. Another advantageous feature is that by providing apertures 324 and 326 in the member 320 which align with the features 114 and 116 in the housing 110, fewer fasteners are need to secure the member 320 in place, since the fasteners which secure the clam shell halves of the housing 110 together may also be used to secure the member 320 in place.

According to an exemplary embodiment, the member 320 is intended to be configured such that lateral forces are transmitted through the flat or planar portion 330 into the legs 332, 334 and into ribs extending from the features 114, 116 provided in the housing 110. In this manner, lateral forces may be transmitted into a relatively strong structural area of the housing 110.

It is important to note that the construction and arrangement of the power tool and shaft lock mechanism as shown in the various exemplary embodiments is illustrative only. Although only a few embodiments of the present inventions have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present invention as defined in the appended claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present inventions as expressed in the appended claims. 

1. A power tool having a tool shaft and a mechanism for restricting movement of the tool shaft, the mechanism comprising: a pin configured to engage the tool shaft to restrict movement of the tool shaft; and a member provided adjacent the tool shaft and fastened to a housing of the power tool to prevent movement of the member, the member comprising an aperture through which the pin extends when the pin engages the tool shaft.
 2. The power tool of claim 1, wherein the tool shaft comprises an aperture and the pin is configured for selective insertion into the aperture to restrict movement of the shaft.
 3. The power tool of claim 1, wherein the member is configured to transmit a load from the pin to an area of the housing.
 4. The power tool of claim 1, further comprising a button coupled to the pin for allowing a user of the power tool to activate the mechanism.
 5. The power tool of claim 4, further comprising a spring for biasing the pin and the button away from the tool shaft.
 6. The power tool of claim 1, wherein the member comprises an aperture for receiving a feature of the housing to assist in the proper positioning of the member in the housing during assembly of the power tool.
 7. The power tool of claim 1, wherein the housing comprises at least two portions coupled together and the mechanism is provided substantially entirely within one of the at least two portions.
 8. The power tool of claim 1, wherein the housing comprises at least two portions and the fastener both couples the member to the housing and couples the two portions of the housing together.
 9. The power tool of claim 1, further comprising at least one rib provided in the housing to restrain movement of the member when a force is applied to the member by the pin.
 10. The power tool of claim 1, wherein the member is a plate having at least one tapered end.
 11. The power tool of claim 1, wherein the pin restricts rotation of the tool shaft.
 12. The power tool of claim 1, wherein the member is fastened to the housing with a fastener that is selected from the group consisting of a screw and a bolt.
 13. The power tool of claim 1, wherein the member is fastened to the housing by hot staking the member to the housing.
 14. The power tool of claim 1, wherein the member is provided approximately 10.5 millimeters from a rotational axis of the tool shaft.
 15. The power tool of claim 1, wherein the member is formed of a metal.
 16. A power tool comprising: a rotatable shaft having an opening provided therein; a device for preventing rotation of the shaft during attachment of an accessory to the shaft, the device comprising a rod configured for selective insertion into the opening to prevent rotation of the shaft and a plate having an aperture provided therein through which the rod extends during insertion of the rod into the opening; wherein the plate is fastened to the power tool with a fastener configured to prevent movement of the plate and is configured to transmit a load from the rod when a user attaches an accessory to the shaft.
 17. The power tool of claim 16, further comprising a spring for biasing the rod away from the opening.
 18. The power tool of claim 16, wherein the accessory comprises a tool bit.
 19. The power tool of claim 16, further comprising means for moving the rod into the opening.
 20. The power tool of claim 16, wherein the plate includes at least two apertures for attaching the plate to a housing of the power tool.
 21. The power tool of claim 16, wherein the plate is formed of a metal.
 22. The power tool of claim 21, wherein the metal is a steel.
 23. The power tool of claim 16, wherein the power tool is a rotary cutting tool.
 24. The power tool of claim 23, wherein the power tool is a battery-powered tool.
 25. The power tool of claim 16, wherein the plate is provided such that it is approximately 10.5 millimeters from a central longitudinal axis of the rotatable shaft.
 26. A power tool having a mechanism for preventing free rotation of a tool shaft during attachment of an accessory to the tool shaft comprising: a tool shaft having an aperture extending at least partially through the tool shaft in a direction transverse to a central longitudinal axis of the tool shaft; a pin configured for selective movement between a first position in which a portion of the pin is in the aperture and a second position in which the portion of the pin is not in the aperture; and a metal member provided adjacent the tool shaft and having an aperture through which the pin extends in the first position, the metal member secured to the power tool with at least one fastener to prevent movement of the metal member; wherein the tool shaft is prevented from freely rotating when the pin is in the first position and is not prevented from freely rotating when the pin is in the second position.
 27. The power tool of claim 26, wherein the accessory is a tool bit.
 28. The power tool of claim 26, wherein the aperture extends completely through the tool shaft.
 29. The power tool of claim 26, wherein the pin is generally cylindrical.
 30. The power tool of claim 26, wherein the pin has a tapered end.
 31. The power tool of claim 26, wherein the metal member comprises a generally planar plate.
 32. The power tool of claim 26, wherein the metal member comprises a generally planar plate having at least one extension with an aperture provided therein for securing the metal member to the power tool.
 33. The power tool of claim 26, wherein the power tool comprises a housing having two pieces and the metal member is secured to one of the two pieces with the at least one fastener.
 34. The power tool of claim 26, wherein the power tool is a battery-powered tool. 